The casings for conventional relays for sealingly receiving an electromagnet unit and a contact unit are typically provided with the shape of an elongated box. The casing is provided with an opening in its upper face for receiving an electromagnet, and a contact unit is typically fitted upon the casing from above. The armature of the electromagnet unit is typically L-shaped and is provided with a first portion extending in parallel with the electromagnet and a second portion extending across the magnetic gap defined between an end of the electromagnet and an adjacent end of a yoke associated therewith. The second portion of the armature is adapted to move so as to close and open the magnetic gap with the bending line of the armature resting upon an edge of the yoke acting as a hinge.
According to such a structure, since the electromagnet unit and the contact unit must be put together before they may be fitted into the casing, the assembly work requires skill and, in particular, is not very suitable to be performed with an automated assembly machine. As a matter of fact, when the assembly consisting of an electromagnet and a contact unit is to be fitted into a casing, the terminal pins extending from the contact unit must be passed through corresponding holes provided in the casing, and there is a chance of bending the terminal pins and thereby creating defective products when forcing the terminal pins into such holes with an automated machine.